Hildern steals other people's research and claims it as his own, as well as send mercs to their deaths to cover his own @ss
McLafferty engages in corporate espionage practically as a hobby. The Van Graffs are violent thugs who gun people down in their own store. Both slaughter rivals as a matter of course, and have senators in Shady Sands protecting them
Curtis sold out to the Legion.
The ideals of the NCR are fine. But people are perverting the cause. Which is the point. The NCR isn't exactly living up to the ideals behind it. Even staunch NCR defenders in the game like Boone and Cass admit this.
All of that is true, the NCR is far from perfect.
The thing is, compared to most other governments in the series, it's still much better. We can make a case that House is an able administrator that doesn't want to restrict civil liberties overmuch, but he is uuterly ruthless against anyone that doesn,t take his side (see how he attacks the Kings in most ending scenarios). I also do not buy for a second that he's as good as he claims, and that he alone should be entrusted with the future of New Vegas.
Beyond House, what is there? The Legion, a bunch of cartoonishly evil, murderous rapists? The Boomers, jingoists who literally blow up everyone else? The Brotherhood, fanatics who kill and steal in the name of their Code? The Khans, glorified thugs and drug dealers? To say nothing of the Enclave which tried to exterminate almost the entire planet.
Maybe an intelligent Courier would count too, as ruler of an independant Vegas. But beyond that, flawed as NCR is, you have precious few viable options.